This is true. Some of them (though I think less now, excluding any new chemicals that have been employed recently) have cancer-inducing chemicals in them, and when you put them around high-absorption areas like the armpit, they get introduced straight into you. The chemical mimics estrogen, and, particularly in women, seems to have some correlation with increased breast cancer, which increased estrogen levels in those areas of the body correlate with naturally.
I use toms deodarant, their ingredients arent harmful from my research